1. Field of the Invention
The invention relates in general to elevator systems, and more specifically to new and improved car call entry and display stations for entering calls for desired destination floors. The invention also relates to new and improved apparatus for monitoring a plurality of switches.
2. Description of the Prior Art
It is conventional in elevator systems to provide at least one car call entry and display station in each elevator car for registering car calls for desired destination floors of the passengers. The car call station includes a plurality of switches, usually pushbuttons, along with identifying notations which indicate the floor each switch is associated with. The plurality of switches are arranged in a square or rectangular format, with the switch at the lower left-hand corner usually being associated with the lowest floor in the building, and the switch at the upper right-hand corner usually being associated with the highest floor in the building. The switches may be numbered horizontally, or vertically, as specified by the building architect.
The stationary contacts of the pushbuttons may be the conventional discrete contacts of a conventional discrete pushbutton; or, the stationary contacts of all of the pushbuttons may be etched or plated on a common printed circuit board. The stationary contacts of the switches may be connected in parallel, or they may be connected in a matrix which is scanned, for either the discrete pushbutton arrangement, or the printed circuit board arrangement of the switches. The means for operating each switch is preferably a movable contact which, when depressed, forms a direct metallic connection between the stationary contacts, or it may simply move a movable contact closer to the stationary contacts to change their capacitive relationship. In the latter arrangement, the change in capacitance is utilized to detect operation of the pushbutton. A movable contact is preferred since it does not depend upon body capacitance to earth ground, and it is thus not difficult to operate by a person wearing gloves, and it is not subject to false operation by ionized air during a fire, which creates an electrical path from the switch to earth ground. However, proximity or touch contact switches with no movable electrodes may be used in combination with a smoke and/or heat sensor which disables the car call switches and returns the elevator car to a specified floor.
Regardless of the type of switch used, and the type of interconnections between the switches, it would be desirable to standardize the factory wiring of the car call station, and to standardize the connections which are made to the car call station in the field. The printing of the stationary contacts of all of the pushbuttons on a common printed circuit board, and their interconnection in a matrix, is a step in the direction of simplifying and standardizing the shop and field wiring. However, the advantages of such batch fabrication are offset by the fact that the notations on the switches identifying the floor they are associated with may run horizontally on one elevator installation, and vertically on the next, depending upon the specifications of the building architect. Also, when the building has fewer floors than the number of switches disposed on the common printed circuit board, the wiring of a matrix printed circuit board switch arrangement would be non-standard, as only certain switches on the printed circuit board would be used, and the notations on these selected switches may run horizontally, or vertically, as specified.